FWG plant trouble shooting

Problem

Cause

Action

Low Sea Cooling water/Ejector pump flow / pressure. Minimum pressure 300 kPa. At inlet side of ejector.

Too low ejector pump pressure.

Clean, or replace pressure gauge.

Suction strainer blocked.

Clean suction strainer.

Valves on suction or pressure pipe defect.

Examine and overhaul defective valves.

Leakage from suction pipe to pump.

Repair.

Impeller / wear ring defective.

Check pump maximum clearance.

Clocked up condenser plate stuck.

Dismantle condenser plate stack and clean.

Pump rotating in wrong direction.

Interchange phases.

Sight glass overflow. Normal back pressure for freshwater pump is 120…160 kPa

Suction pipe leakage.

Check suction pipe especially
unions and connections. Repair.

Mechanical seal in freshwater pump defect.

Replace mechanical seal.

Impeller / seal ring in freshwater extraction pipe defect.

Check pump maximum clearance.

Pump rotating in wrong direction.

Interchange phases.

Valves to freshwater tank
closed.

Check all valves.

Inlet filter for water clock blocked.

Clean filter.

Salinity too high (more than 2.0 ppm).

Demister not fitted correctly

Check that demister is fitted
against baffle and front cover.

Front cover gasket defect or not fitted correctly.

Replace front cover gasket.

Insufficient brine extraction.

Check sea water ejector pump end ejector itself.

Electrode unit defective or
dirty.

Examine electrode unit for
cracks. Check that it is fitted
correctly. Clean, if necessary.

Leakage in condenser section

Open FWG and pressure test condenser. Max. 600 kPa. If there is defective plate, remove together with adjacent plate assemble plate stack according to new plate number with reduced assembly measurements. Check plates gaskets and replace, if necessary.

Insufficient brine extraction – brine level in sight glass higher than 20 mm

Too low ejector pump pressure.

See special instructions for “Low Sea Cooling water/Ejector pump flow / pressure” above.

Foreign bodies in ejector nozzles.

Check nozzles and clean. Replace nozzles, if damaged.

Too high back pressure down-stream of ejector.

Examine overboard pipe and valves.

Wrong dimension of feedwater orifice.

Examine orifice dimension – check technical specification.

Non-return valve in brine suction pipe of ejector defected.

Examine valve and repair or replace.

Frequent refill of freshwater expansion tank due too loss of hot water

Leakage in evaporator section.

Open FWG and pressure test condenser. Max. 600 kPa. If
there is defective plate, remove together with adjacent plate assemble plate stack according to new plate number with reduced assembly measurements. Check plates gaskets and replace, if necessary.

Abnormal amperage consumption of ejector pump motor.

Ejector nozzles defective.

Replace nozzles.

Wrong dimension of feedwater orifice.

Check dimension and replace if necessary.

Bearings in motor defective.

Examine with stetoscope and replace bearings if defective.

Contactor defective.

Examine and replace contactor set if defective.

Breaking of phases.

Max. 5 %difference in amperage between phases.

Drop in production.

Partially blocked feed water orifice and/or sludge deposits on hot water side.

Dismantle evaporator section, and clean evaporator and orifice.

Sludge on the heat exchanger plates on the sea water side.

Dismantle condenser section, and clean.

Inlet channel in evaporator/ condenser plate stack blocked, e.g. with rust scales, gasket fragments etc.

Dismantle evaporator/ condenser section, and clean.

Drop in production.

Too low ejector pump pressure.

See instructions for “Low Sea Cooling water/Ejector pump flow / pressure” above.

Leakages

Carry out a pressure test at
max. 150 kPa

Foreign bodies in ejector nozzles.

Check nozzles and clean. Replace nozzles, if damaged.

Too high back pressure on ejector outlet side. Max 60 kPa.

Check overboard pipe and valves for blocking/ functionability

Non-return valve in air extraction pipe defect.

Replace non-return valve.

Hot water temperature too
high.

Reduce to specified temperature.

Defective water clock.

Examine water clock. Let the produced water flow through water clock into a 10 l pail, and check production with a stop
watch.

Problem

Cause

Action

Evaporating temperature has dropped.

Hot water temperature is low.

Increase the temperature to the specified level.

Hot water flow rate is too low.

Increase the hot water flow rate.

Distillate generation rate has dropped.

Inside the heating tube is fouled up.

Clean the heater piping.

Inside the condenser piping is fouled up.

Clean the condenser piping.

Hot water temperature is low.

See the relevant instruction.

Hot water flow rate is too low.

Increase the hot water flow rate.

Cooling water flow rate is too low.

Increase the cooling water flow rate.

Sight glass is filled with water.

See the relevant instruction.

Degree of vacuum in the evaporator has dropped.

See the relevant instruction.

Degree of vacuum in the evaporator has dropped.

Air is leaking.

Repair the leaking area, and perform air test at 0.05 MPa.

Water ejector has malfunctioned.

See the relevant instruction.

Water ejector has malfunctioned.

Nozzle is clogged.

Clean the nozzle

Diffuser has been corroded or worn out.

Replace with a new one.

Nozzle has been worn out.

Replace with a new one.

Outlet pressure is 0.08 MPa or higher.

Check for the clogging of the ejector outlet piping; check the valve opening of the overboard discharge valve.

Outlet pressure is negative.

Somewhat close the overboard discharge valve.

Sight glass is filled with distillate.

Distillate pump has failed.

Repair the distillate pump.

Distillate pump outlet valve is in the closed position.

Open the distillate pump outlet valve.

Outlet piping is clogged.

Clean the outlet piping.

Distillate pump is drawing air.

Replace the mechanical seal; or see the instruction for the pump.

Salinity of distillate is too high.

Distillate generation rate is too high.

Decrease the hot water flow rate.

Evaporating temperature is too low (50 °C or lower).

Somewhat close the vacuum adjust valve to increase the evaporating temperature.

The FWG has been used in a port or river mount, and the feed water is dirty.

Stop running the FWG

Indication on the salinity indicator is faulty.

Check using the salinity indicator test switch.

Clean the cell (electrode).

Condenser piping has been damaged.

Plug a failed pipe.

Feed water flow rate is lower than the specified level.

Opening of the feed water adjust valve is insufficient.

Adjust the opening of the feed water adjust valve.

Feed water orifice is clogged.

Open and clean the feed water orifice.

Internal pressure on the condenser piping is insufficient.

Somewhat close the condenser cooling water outlet valve.

Feed water flow rate is higher than the specified level.

Opening of the feed water adjust valve is excessively large

Somewhat close the opening of the feed water adjust valve.

Feed water orifice has been worn.

Replace the feed water orifice.

Pump does not start.

Motor or electrical system has failed.

Inspect and repair.

Impeller has seized with the casing ring. The pump has seized.

Replace or repair the impeller; replace the casing ring.

Check centering of the motor with the pump.

Check the eccentricity of the shafts. Inspect the bearings.

Inspect balance on the impeller. Inspect the ring groove on the casing.

Inspect the shaft coupling.

Pump fails to attain the specified capacity and head.

Pump is drawing air.

Check the suction system. Retighten.

Inspect and retighten the joint for the included instrumentation as well as the valve spindle.

Suction pipe strainer is clogged.

Clean.

Impeller passage is blocked.

Clean.

Check the casing, impeller, etc. for any damage.

Clean the strainer.

Clean the suction and discharge piping.

Consider replacement of the strainer mesh.

Motor is running in the reverse direction.

Correctly connect the wires.

Motor speed has dropped.

Check the electrical system.

Clearance to the casing ring has increased.

Replace the casing ring; repair or replace the impeller.

Adjust the centering with the motor.

Inspect the ball bearing.

Inspect balance on the impeller. Check the eccentricity of the shafts.

Inspect the shaft coupling.

Impeller has been damaged.

Replace the impeller.

Inspect the casing.

Inspect the shaft.

Inspect the inside of the casing.

Pump has failed. Water flows immediately after start but stops soon.

Air is trapped in the suction pipe.

Correct the piping. Check the air outlet valve. Inspect the suction pipe.

Air is drawn through the stuffing box.

Inspect the mechanical seal. Inspect the seal line.

Pump has failed.

Motor is overloaded.

Bearing has been damaged.

Replace the bearing. Adjust the centering between the motor and the pump. Inspect the shaft coupling. Inspect and resupply the lubricant.

Motor is misaligned with the pump.

Adjust the centering. Inspect the shaft coupling. Inspect the bearing.

Shaft has been deformed.

Replace the shaft. Adjust the centering between the motor and the pump. Inspect the shaft coupling. Inspect the bearing.

Motor or electrical system is faulty.

Inspect and repair.

Amount of discharge is too much.

Somewhat close the valve on the discharge side.

Pump is vibrating.

Impeller is not balanced.

Repair or replace the impeller.

Inspect the casing ring.

Inspect the balance of the impeller.

Inspect the bearing.

Bearing has been damaged.

Replace the bearing.

Adjust the centering between the motor and the pump. Inspect the shaft coupling. Inspect and resupply the lubricant.

Motor is misaligned with the pump.

Adjust the centering. Inspect the shaft coupling. Inspect the bearing.

Shaft has been deformed.

Replace the shaft.

Adjust the centering between the motor and the pump. Inspect the shaft coupling. Inspect the bearing.

Pump has been incorrectly installed.

Investigate into the state of installation, and correctly install the pump.

Pump has failed.

Bearing is overheated

Bearing has been poorly assembled.

Open and adjust the bearing.

Inspect the shaft. Fill fresh lubricant.

Motor is misaligned with the pump.

Adjust the centering.

Inspect the shaft coupling.

Shaft has been deformed.

Replace the shaft.

Adjust the centering between the motor and the pump. Inspect the shaft coupling. Inspect and resupply the lubricant.

Thrust being exerted onto the bearing is greater than planned.

Repair or replace the impeller.

Inspect the casing ring.

Check if the balance hole of the impeller is blocked.

Inspect the bearing.